RESENTED here are the results of a series of tests designed to investigate the reasons for the variation in octane-number requirements of engines.
The author comes to the following conclusions:
Practically everything with which an engine comes in contact has an effect on its requirement, hence it is highly unlikely that all engines of a given make and model will ever have the same requirement.
Study of the effects of various types of fuels and lubricants offers interesting possibilities for the reduction of the requirement increase due to deposition.
Variations in the requirement from engine to engine can be minimized by careful attention to engine adjustments.
Test work to evaluate the requirement will be more consistent and reproducible if not only are all necessary engine adjustments made but also the tests are conducted under conditions of substantially constant atmospheric temperature, pressure, and humidity.